The invention pertains to an apparatus for manipulating (and supporting in a retracted position) an organ such as a beating heart. Preferred embodiments of the invention pertain to an apparatus for support and manipulation of a beating heart during surgery thereon, in a manner promoting oxygenation during the surgery.
Coronary artery bypass grafting (CABG) has traditionally been performed with the use of a cardiopulmonary bypass (CPB) machine to oxgenate and perfuse the body during surgery. Recently, techniques have been developed to allow for performing CABG without the use of CPB by stabilizing the epicardial surface of a beating heart at the coronary anastomotic site with a stabilizer (e.g., stabilizing feet) to allow placement of sutures through the graft vessel and recipient coronary artery. This procedure may be performed through a partial or full sternotomy, or via a thoracotomy (which is an incision between two adjacent ribs).
Access to the left anterior descending (LAD) coronary artery is easily performed by either a sternotomy or a thoracotomy. However, the patient typically requires bypass to multiple coronary arteries, including the circumflex artery (CxA) on the left lateral aspect of the heart, the right coronary artery (RCA) on the right lateral aspect of the heart, and the posterior descending artery (PDA) on the back side of the heart. It is very difficult to access the CxA, RCA, and PDA without a sternotomy, as the heart needs to be turned or tilted (or turned and tilted) significantly to reach its side or back, and with an intact sternum, insufficient space exists for these maneuvers. For example, the apex of the heart is generally lifted out of the body through a sternotomy in order to reach the PDA. Surgeons often place the patient in a Trendelenberg position, with the operating table tilted so that the patient""s head lies lower than the feet with the patient in supine position, in order to assist with lifting the heart up and back.
An additional challenge to beating heart surgery is that some hearts do not tolerate manipulation well from a hemodynamic standpoint. The potential exists with current manipulation techniques to compress the heart (e.g., by pressing it with stabilization feet) or great vessels in such a way that hemodynamic function is compromised.
There is a need for a beating heart retraction apparatus capable of physically translating a beating heart from its natural resting place to a location better suited to surgical access, and then holding the beating heart in the latter location during surgery without compressing (or otherwise deforming) the heart or great vessels in such a way that hemodynamic function is compromised.
Typically, beating heart surgery has been accomplished through a partial sternotomy using pericardial sutures to retract the heart into the proper position for surgery, and using a stabilization apparatus (e.g., stabilizing feet) to stabilize the portion of the heart surface to be cut. Sometimes, surgery is performed on the properly positioned heart without using a stabilization apparatus.
However, conventional use of pericardial sutures for retraction of a beating heart has limitations and disadvantages including the following. It is inconvenient and potentially harmful to the patient to incise the pericardium and insert sutures along cut edges of the pericardium, and then exert tension on the sutures to move the heart together as a unit with the pericardium. When the sutures are pulled to lift the heart (with pericardium), compressive force exerted by the pericardium on at least one side of the heart sometimes constrains cardiac contraction and expansion.
There are three distinct stages involved in preparing an artery (on an organ) for anastomosis:
1. gross manipulation: the organ is physically translated from its natural resting place to a location better suited to surgical access;
2. artery presentation: the target artery on the organ is identified and the position of the organ is finely adjusted so that the target artery is approachable; and
3. artery stabilization: the target artery and surrounding tissues are immobilized, allowing fine surgical techniques on very small features.
The present invention pertains to an improved method and apparatus for retraction (gross movement) of a beating heart or other organ into a desired position and orientation to allow surgery to be performed on the organ. When the organ has been retracted (in accordance with the invention) into a desired position and orientation, any of the many commercially available tissue stabilization products (including those marketed by Guidant, Medtronic, CardioThoracic Systems, and Ethicon) can be used to stabilize a portion of the organ""s surface on which surgery is to be performed. However, such tissue stabilization products cannot duplicate the function of the inventive apparatus. Retraction requires lifting and usually rotation of the organ. Devices designed specifically for tissue stabilization are not well suited to those motions.
One class of the stabilization devices commonly used to stabilize a target portion of a heart surface (a portion on which surgery is to be performed) are the stabilization devices that comprise rigid (C-shaped or linear) structures lined with suction cups, such as those described in the article Borst, et al., xe2x80x9cCoronary Artery Bypass Grafting Without Cardiopulmonary Bypass and Without Interruption of Native Coronary Flow Using a Novel Anastomosis Site Restraining Device (xe2x80x9cOctopusxe2x80x9d), J. of the American College of Cardiology, Vol. 27, No. 6, pp. 1356-1364, May 1996. The stabilization devices described in the Borst, et al. article are marketed by Medtronic, Inc. and are known as xe2x80x9cOctopusxe2x80x9d devices.
It has been proposed to use such an Octopus device to retract the heart into a desired position for surgery (and hold the retracted heart in this position), as well as to stabilize a portion of the heart""s surface following retraction (gross movement) of the heart. See, for example, PCT International Application WO97/10753 (by Medtronic, Inc.) entitled xe2x80x9cMethod and Apparatus for Temporarily Immobilizing a Local Area of Tissue,xe2x80x9d published Mar. 27, 1997, especially with reference to FIG. 33 thereof. However, no conventional Octopus device can support a beating heart with adequate compliance to allow normal heart beating movement, and instead each conventional Octopus device would exert compressive or twisting force on at least one side of the beating heart, thereby constraining cardiac contraction and expansion. Also, one of the small-diameter suction cups of a conventional Octopus device would be too small to reliably grip (and support) the heart without causing trauma to the heart surface. Thus, in order to reliably (but atraumatically) retract and support the heart in the retracted position, many small-diameter suction cups (supported on a rigid frame which frame is itself rigidly supported) need to exert suction simultaneously on the heart, which exacerbates the problem of constrained cardiac contraction and expansion due to the exertion of compressive or twisting force on the heart.
The apparatus of the invention differs in purpose and form from conventional tissue stabilization devices. The purpose of the inventive apparatus is to move an organ grossly from one position to another and maintain the organ in the final position (without significantly constraining cardiac contraction and expansion). The inventive apparatus is not designed to stabilize specific areas of the organ. The shape and nature of the suction cup (or other suction member) of the inventive apparatus differ from the suction cups of conventional tissue stabilization devices in the need to accommodate different anatomy. For example, the inventive suction member can be larger than a conventional tissue stabilization device. Also, since the inventive apparatus exerts suction over a larger surface area of organ tissue, the required pressure differential can be less than that required by conventional tissue stabilization devices. The low-pressure differential has a clinical benefit in that the potential for creation of hematomas is lessened.
U.S. Pat. No. 5,799,661, issued Sep. 1, 1998 to Boyd, et al. (and assigned to Heartport, Inc.) describes (with reference to FIGS. 33A-33C) a suction cup manipulator on a long shaft. The suction cup is to be attached to an arrested heart by suction, and the device is then manipulated to move the heart around in the chest cavity. A vacuum is applied to the cup to provide suction, and the vacuum is said preferably to have a value not less than xe2x88x92150 mmHg (to avoid tissue damage). The suction cup is made of a soft, flexible elastomeric material such as silicone rubber, has a diameter of approximately 12 mm to 50 mm, and has a textured, high friction distal surface (for gripping the heart). The high friction can be achieved by a pattern of bumps or an absorbent high friction material (such as nonwoven polyester fabric). A disadvantage of the bumps is that they would likely cause trauma to the organ being manipulated (even with a vacuum in the preferred range).
U.S. Pat. No. 5,799,661 suggests without explanation that the suction cup is flexibly mounted to the distal end of a rigid shaft, but it is apparent from FIGS. 33A-33B that this simply means that the cup itself has some flexibility so that the cup can bend relative to the rigid shaft. U.S. Pat. No. 5,799,661 does not teach attaching the suction cup to the shaft by a joint which provides limited freedom to translate along a first axis and/or full (or at least limited) freedom to rotate about the first axis, but no significant freedom to translate in directions perpendicular to the first axis. Thus, the suction cup apparatus described in U.S. Pat. No. 5,799,611 is useful only to retract an arrested heart; not a beating heart or other moving organ since the suction cup apparatus of U.S. Pat. No. 5,799,611 does not have compliance to allow for normal organ movement such as a heart beat, and would instead exert compressive or twisting force on at least one side of the moving organ, thereby constraining cardiac contraction and expansion or other normal organ movement.
U.S. Pat. No. 5,782,746, issued Jul. 21, 1998, discloses an annular suction device for immobilizing part of the surface of a heart during surgery. Although the device is said to allow the heart to beat in a xe2x80x9crelatively normalxe2x80x9d manner during surgery, the device is rigidly mounted to a fixed mounting structure during surgery, and thus neither the device nor the part of the heart surface which it immobilizes would have freedom to move significantly relative to the mounting structure during surgery. The reference suggests positioning the device on the heart, applying vacuum to the device to cause it to exert suction on the heart, then moving the device to xe2x80x9cpartiallyxe2x80x9d raise the heart, and then rigidly mounting the device to the fixed mounting structure so that the device supports the xe2x80x9cpartially raisedxe2x80x9d heart during surgery.
A key difference between the inventive apparatus and both conventional apparatus for tissue stabilization and conventional apparatus for organ retraction is that the inventive apparatus provides system compliance that allows the target organ to maintain normal motion (e.g., normal compression and expansion in the case that the organ is a beating heart). In the case of a beating heart, this compliance provides distinct clinical value by lessening the negative impact of manipulation on hemodynamics.
In a class of embodiments, the invention is an organ manipulator including at least one suction member (e.g., a suction cup) and preferably also a compliant joint to which the suction member is mounted. The compliant joint provides built-in system compliance so that when the suction member supports an organ (e.g., a beating heart) by suction, the suction member does not constrain normal motion of the organ (e.g., normal beating motion of the heart), either during gross movement of the organ into a retracted position or during surgery with the organ attached to or held by the suction member in the retracted position. In preferred embodiments the suction member is shaped and configured to retract a beating heart and suspend it in the retracted position during surgery. As the suspended heart beats, the compliant joint allows the heart to expand and contract freely (and otherwise move naturally) so that hemodynamic function is not compromised. Suspension of the beating heart below the suction member tends to expand the heart chambers, which in turn tends to reduce the amount of compressive deformation of the heart and great vessels which would otherwise result from pressing the heart with a stabilization device (such as stabilization feet) during surgery, so that the invention assists in oxygenation during surgery.
The suction member conforms (or, in some embodiments can be deformed to conform) to the anatomy of the organ. Preferably, its inner surface is smooth, concave, and lined with absorbent material to improve traction without causing trauma to the organ (e.g., bruising) during retraction from one position to another within the body cavity. Preferably, the suction member is a suction cup having a foam seal mounted around the cup""s periphery.
Coupling a vacuum source to the suction member (with the member applied to the organ surface) creates a differential in pressure between the inner and outer surfaces of the member. The pressure differential forces the suction member and organ surface together in such a manner as to create traction between the two. As a result of the traction, the surface of the organ will move with the suction member. The device holds the organ with sufficient force to allow retraction using suction, and to maintain the organ in the desired position (i.e., by suspending it from the suction member) during surgery.
In preferred embodiments, the compliant joint couples the suction member to an arm (which is rigid or can be placed in a rigid state), and the arm is adjustably mounted to a fixed mounting structure. The mounting structure can be a conventional sternal retractor (of the type used to maintain a sternal incision in an open state for cardiac access), an operating table, or another rigid structure. When the organ is attached to or held by (e.g., suspended below) the suction member, the compliant joint gives the suction member freedom to move (at least axially along the axis of the suction member, e.g., vertically when the suction member has a vertical axis) relative to the arm and mounting structure in response to normal organ movement (e.g., beating of a heart) to avoid compromising the normal functioning of the organ. When a beating heart is suspended below the suction member, the compliant joint allows the heart to expand and contract freely (at least vertically) as it beats. Optionally, the compliant joint also gives the organ freedom to rotate about the axis of the suction member (typically, a vertical axis) and/or to swing relative to the arm.
In preferred embodiments, the inventive apparatus provides for compliant retraction of a beating heart (or other organ) in the sense that it retracts the organ via suction, while allowing normal myocardial movement (or other normal organ movement) in at least the vertical direction, and optionally also allowing normal organ movement perpendicular to the vertical direction (e.g., pivoting or twisting motion about a vertical axis). In some such preferred embodiments, the compliant joint is a sliding ball joint attached to a movable arm, and the arm can be locked in any of a variety of positions (relative to a fixed supporting structure) to allow adjustable degrees of organ retraction. The compliance provided by the ball joint allows the organ to better tolerate manipulation.
Preferably, the suction member is specially designed to decrease trauma to the heart muscle (or other organ tissue) during attachment, and the apparatus is preferably implemented to have one or more of the following features: an absorbent cup lining for increased holding power, a smooth and soft inner cup surface to decrease myocardial bruising (hematoma formation) and to diffuse the suction across the cup, a means for regulation of suction intensity, and a vacuum accumulator in the suction line to decrease immediate loss of holding power with variations in vacuum supply.
In other embodiments, the inventive apparatus includes multiple suction members (e.g., multiple suction cups) mounted on the ends of retracting fingers for gripping an organ, with the fingers implementing a compliant joint. In other alternative embodiments, the inventive apparatus includes a bio-absorbable disc with an adhesive surface to be adhered to the heart or other organ (instead of a suction member), with the disc preferably being mounted to a compliant joint.
In other embodiments, the invention is a method for compliant retraction of an organ, including the steps of retracting the organ using suction, and supporting the organ in the retracted position using suction, in such a manner that the organ has freedom to move normally (e.g., to beat or undergo other limited-amplitude motion) at least in the direction in which the suction is exerted during both steps. In some such embodiments, the method includes the steps of retracting the organ using suction, and suspending the organ in the retracted position using suction, in such a manner that the organ has freedom to move normally (e.g., to beat or undergo other limited-amplitude motion) in at least the vertical direction during both steps. One embodiment is a method for retracting a beating heart, including the steps of affixing a suction member (e.g., a suction cup) to the heart at a position concentric with the apex of the heart (preferably the suction member has sufficient curvature to conform with the apex and is shaped to be at least generally symmetric with the apex) and applying suction to the heart (e.g., by coupling the suction member to a vacuum source), and moving the suction member to retract the heart to a desired position for surgery such that the heart has freedom to undergo normal beating motion (at least along the axis of the suction member) during retraction. Preferably, the suction member is mounted to a fixed assembly (e.g., a fixedly mounted sternal retractor) by a compliant joint in such a manner that the suction member does not constrain normal beating motion of the heart, either during gross movement of the member (with heart) into the desired position or while the heart is supported by (e.g., suspended vertically below) the member during surgery in such position. In such preferred embodiments, as the heart beats, it is free to expand and contract normally (with the compliant joint allowing the suction member to oscillate along the axis of the suction member, and optionally also to twist about such axis) so that hemodynamic function is not compromised.
Other aspects of the invention are a flexible locking attachment arm (having both a flexible state and a rigid state) to which the inventive suction member (or compliant joint) is mounted, and an organ manipulator including such a locking arm and at least one suction member (or compliant joint and suction member) mounted to the arm.